Question
What is the 'Land uses' feature in MIKE+ Rainfall Runoff model and how is it used?
Answer
The ‘Land uses’ feature is located in the ‘Catchments’ editor and allows the user to specify the spatial distribution (as proportions) of land uses within a catchment and thereby compute runoff in a more realistic way. When applying this feature the user must specify (manually or in an automated way) the contributing area of each land use within each catchment and also set the losses and infiltration properties for each land use in the ‘Land uses’ editor. The land use distribution functionality gets activated in the ‘Catchments’ editor (‘General’ tab) after enabling the “Use land use distribution” checkbox - see Fig. 1.
Fig. 1 - Land Use Distribution activation.
After enabling the “Use land use distribution” option, the additional ‘Land uses’ table, at the centre, must be populated with appropriate ID values and associated contributing areas for each Land use - see Fig. 2.
Fig. 2 - Land use coverage percentage distribution within each catchment.
Note: The ‘Land uses’ functionality is only available with the Hydrological models of ‘Time Area’, ‘Kinematic Wave’, ‘Linear Reservoir (C1 and C2)’, and ‘RDI’, but not the ‘UHM’ model.
When the user is applying any of the hydrological models ‘Time Area’, ‘Kinematic Wave’ or ‘Linear Reservoir (C1 and C2)’ for a given catchment, the relevant Land uses IDs (see Fig. 3) may be selected by clicking on the “Insert all” or “Insert” buttons, next to the ‘Land uses’ table.
Fig. 3 - Land uses IDs for each (non-RDI) catchment can be selected in the ID selector pop-up dialog.
Surface losses, roughness and infiltration parameters may then be inserted or modified for each land use ID (also new Land use IDs can be created) in the “Land uses” editor as shown in Fig. 4.
Fig. 4 - Surface losses and infiltration parameters for each land use need to be specified in the “Land uses” editor.
Note: In order to calculate imperviousness, distribution of land uses, time of concentration or other hydrological parameters for Time-Area runoff models (or to calculate imperviousness and catchment width for SWMM hydrological models) in an automated way, one can apply the “Catchment processing” tool (accessed from the ‘Catchments’ menu and ‘Catchment toolbox’ ribbon) - see Fig. 5.
Fig. 5 - Surface losses and infiltration parameters for each land use need to be specified in the “Land uses” editor.
If the user is applying the ‘RDI’ hydrological model for a given catchment, then the relevant RDI parameter sets may be selected by clicking on the “Insert all” or “Insert” buttons. The user then specifies the Parameters RDI ID for each catchment as shown in Fig. 6.
Fig. 6 - RDI parameter sets for each catchment (that includes the RDI hydrological model) can also be selected in the ID selector pop-up dialog.
RDI parameters for each catchment (and new RDI parameters sets) may be defined at the “Parameters RDI” editor as shown in Fig. 7.
Fig. 7 - RDI parameter sets are defined in the “Parameters RDI” editor.
If the user is applying a ‘combined’ hydrological model that includes RDI (e.g. “Kinematic Wave (B) + RDI”) for a given catchment, then the available Land uses IDs and RDI parameter sets may again be selected by clicking on the “Insert all” or “Insert” buttons at the “Catchments” editor (‘General’ tab). As illustrated in Fig. 2, the sum of the contributing areas for the Land Uses within each catchment should be equal to 100%, if it does not, the remaining percentage will be shown in the Area not contributing to runoff field - see Fig. 8.
Fig. 8 - Land Use coverage distribution including the RDI catchment and corresponding area not contributing to runoff.
Total runoff for each catchment is calculated for each Land use percentage contributing area, based on the application of the hydrological model of choice.
Note: Runoff output is provided for the entire catchment rather than separately for each land use within the catchment. However, when a surface runoff model (e.g. Time Area) is combined with RDI model, the simulation will compute the runoff for each method (surface runoff model and RDI) separately as if they were different catchments and will then sum the runoff of the surface runoff and RDI models.
Conclusion
Implementing Land use classifications into Catchments hydrological analysis enables the definition of particular characteristics for each contributing area with distinct surface losses, roughness and infiltration properties, as well as RDI parameters, while enhancing the modeler’s understanding of the catchment dynamics! The model can therefore represent more accurately the interactions between land use coverage and runoff generation.
The functionality enables the prediction of the catchment's hydrological response to land use management changes (e.g. urbanization) and climate change, while also making it possible to integrate different hydrological models (i.e. combine ‘surface runoff’ and ‘continuous’ models) and infiltration formulations within each catchment.
FURTHER INFORMATION & USEFUL LINKS
Manuals and User Guides
MIKE+ Collection System
MIKE 1D Reference Manual
Release Notes
MIKEPlus Release Notes